This invention concerns a stable aqueous emulsion of a mixture of one or more alkoxylated alcohols and one or more anionic surfactants and use of the emulsion to inhibit foaming in papermaking processes.
In the manufacture of paper, a cellulosic pulp is first created and then used to make paper. In most cases, undesirable foaming of the process results from the presence of either naturally occurring surface active components that result from the pulping operation or by the use of many of the additives used in development of papers with the desired end use properties. Some examples of naturally occurring surface active components are lignins and fatty and resin acid salts. Some examples of additives used in the papermaking process include starches, fillers, latex binders, wet strength agents and the like. Many of these components either assist in the stabilization of foams or may themselves be contributors to the formation of foams.
Foaming of the cellulosic pulp slurries can be problematic in the manufacture of the finished paper and may impact production and quality of the finished paper. Production of the finished paper may be impeded by the presence of small bubbles within the forming sheet which may impede the removal of water in the sheet. Other production related difficulties occur when the process tanks and pipes used to transport the cellulosic pulp slurry contain substantial amounts of air. The air causes the capacity of the equipment to be compromised since it takes up volume in the equipment meant to handle the cellulosic slurry. The presence of bubbles in the sheet may also cause voids in the continuity of the sheet or may alter the porosity or smoothness of the sheet which are quality aspects generally considered detrimental.
As a result of the foam present during the manufacture of paper, many types of foam abating formulations have been used. Alkoxyalkylated alcohol foam inhibitors are described in German Patent Nos. 2,532,888 and 1,595,369. Neither of these references, however, describes emulsification of the alkoxylalkylated alcohols in water using anionic surfactants.
In its principal aspect, this invention is directed to an aqueous emulsion containing from about 0.1 to about 70 weight percent of a mixture of
a) one or more alkoxylated alcohols of formula
RO(C2H4O)x(C3H6O)yZ
xe2x80x83wherein R is straight or branched C4-C40 alkyl; x is 0 to about 25; y is less than 1 to about 50 and Z is H or the residue of an organic acid, and
b) an effective emulsifying amount of one or more anionic surfactants.
xe2x80x9cAlcohol alkoxy sulfatexe2x80x9d means a compound of formula R3O(R4CH2CH2O)nSO3M where R3 is C8 to C18 alkyl, M is selected from the group consisting of sodium, potassium, magnesium, ammonium, alkanolamine or H, and R4 is absent or CH2. A representative alcohol sulfate is ammonium lauryl ether sulfate.
xe2x80x9cAlcohol sulfatexe2x80x9d means a compound of formula R3OSO3M, where R3 is C8 to C18 alkyl. The alcohol sulfates exist either in the salt form, where M is selected from the group consisting of sodium, potassium, magnesium, ammonium, alkanolamine or H. Representative alcohol sulfates include sodium dodecyl sulfate, sodium tetradecyl sulfate, ammonium lauryl sulfate, magnesium lauryl sulfate, cetyl sulfate, octyl sulfate nonyl sulfate, decyl sulfate, and 4-undeconal, 7-ethyl-2-methyl-sulfate, sodium salt (Niaproof Anionic Surfactant 4, available from Niacet Corporation, Niagra Falls, N.Y.).
xe2x80x9cAlkoxylated alcoholxe2x80x9d means a compound of formula
RO(C2H4O)x(C3H6O)yZ
wherein R is straight or branched C4-C40 alkyl; x is 0 to about 25; y is less than 1 to about 50 and Z is H or the residue of an organic acid.
The alkoxylated alcohols are prepared by reacting a C4-C40 alkyl alcohol, or mixture of C4-C40 alkyl alcohols, both designated herein as ROH, with propylene oxide, and optionally ethylene oxide. The ethylene oxide and propylene oxide may be added in random or block fashion. The resulting alkoxylated alcohol is sparingly soluble or insoluble in water.
Random addition of ethylene oxide and propylene oxide involves both components being added to the alcohol simultaneously, such that the rate of addition to the alcohol is controlled by their relative amounts and reaction rates. Thus, in the case of random addition, it is understood the above formula is not a structural formula but rather is representative only of the molar amounts, x and y, of ethylene oxide and propylene oxide that are added to the alcohol ROH.
In the case of block addition, either the ethylene oxide or propylene oxide is added first to the alcohol and allowed to react. The other component is then added and allowed to react. In the case of block addition, the above formula is representative of the structure of the alkoxylated alcohol, except that the (C2H4O)x and (C3H6O)y groups may be reversed depending on whether the propylene oxide or ethylene oxide is added first.
In an aspect, R is straight or branched C8-C22 alkyl; x is 0 to about 5; and y is less than 1 to about 25.
In another aspect, the alkoxylated alcohol has the following formula:
R1R2CHCH2O(C2H4O)x(C3H6O)yZ
where R1 and R2 are independently C6-C18 alkyl and x, y and Z are defined above.
The preparation of representative alkoxylated alcohols is described in German Patent nos. 2,532,888 and 1,593,369.
xe2x80x9cAlkylxe2x80x9d means a monovalent group derived from a straight or branched chain saturated hydrocarbon by the removal of a single hydrogen atom.
xe2x80x9cAnionic surfactantxe2x80x9d means any anionically-charged surface active agent suitable for stabilizing an emulsion in water of an alkoxylated alcohol. Representative anionic surfactants include, but are not limited to alcohol sulfates, alcohol alkoxy sulfates, polyoxyalkylene phosphate esters and dialkyl sulfosuccinates, sulfosuccinic acid esters with ethoxylated alcohols. The anionic surfactants are available commercially or can be readily manufactured using techniques known in the art. Polyoxyalkylene phosphate esters are preferred. A preferred polyoxyalkylene phosphate ester is the phosphate ester of ethoxylated tridecyl alcohol.
xe2x80x9cDialkyl sulfosuccinatexe2x80x9d means a compound of formula R9OOCCH2(SO3M)COOR10, where R9 and R10 are independently selected from amyl, octyl(2-ethyl hexyl), isobutyl, tridecyl, and lauryl and M is as defined herein. A representative dialkyl sulfosuccinate is dioctylsulfosuccinate.
xe2x80x9cEmulsionxe2x80x9d means a stable, microscopically heterogeneous mixture of two normally immiscible liquid phases, in which one of the liquids forms minute droplets suspended in the other liquid.
xe2x80x9cPhosphate esterxe2x80x9d means a compound of the general formula R3OPO3H2 or R3OPO3R5H, where R3 and R5 are independently C8 to C18 alkyl.
xe2x80x9cPolyoxyalkylene phosphate esterxe2x80x9d means a compound of formula 
and/or 
wherein R6, R7 and R8 are independently C8 to C18 alkyl. Anionic surfactants of the polyoxyalkylene phosphate ester chemistry are complex mixtures and the amount of each type present, i.e., (1), (2), depend upon the process and stoichiometry used with the starting materials.
xe2x80x9cResidue of an organic acid means a group of formulaxe2x80x94C(O)Rxe2x80x2 where Rxe2x80x2 is C1-C4 alkyl.
xe2x80x9cSulfosuccinic acid ester with ethoxylated alcoholsxe2x80x9d means a compound of formula: R11(OCH2CH2)rOCH(SO3M)CH2COOM where R11 is C8-C18 alkyl, r is an integer from 1 to about 10, and M is as defined herein. A representative sulfosuccinic acid ester with ehoxylated alcohol is laureth sulfosuccinate (Schercopol LPS available from Scher Chemicals, Inc., Clifton, N.J.).
The emulsions of this invention contain from about 0.1 to about 70, preferably from about 0.5 to about 20 percent, based on the total weight of the emulsion, of a mixture of one or more alcohol alkoxylates and an effective emulsifying amount of anionic surfactant. The amount of anionic surfactant suitable for preparing a stable emulsion is readily determined empirically by one of ordinary skill in the art. Typically, the amount of anionic surfactant used is between about 0.01 percent and about 10 percent by weight of the alkoxylated alcohol.
The emulsion is prepared by adding an alkoxylated alcohol/anionic surfactant mixture to water and mixing until the desired emulsion is obtained. The mixing may be accomplished by any suitable means such as swirling, stirring or shaking or by mechanically shearing the mixture using a blender, homogenizer, pump, colloid mill, in line mixer, static mixer, propeller, and the like. The emulsion is analyzed by microscopy and/or a particle size analyzer as is known in the art. Typically, the emulsion of this invention has a particle size of from about 2 to about 10 xcexcm.
Preferably, the emulsion is prepared on-site immediately prior to adding to the cellulosic pulp slurry. On-site manufacture of the emulsion allows for easy dosage control and avoids problems generally associated with water-based defoamer compositions due to long storage times and cold temperatures.
In another aspect, this invention is directed to a method of inhibiting foaming in a papermaking process comprising adding to the pulp slurry prior to sheet formation an effective amount of an aqueous emulsion containing from about 0.1 to about 70 weight percent of a mixture of
a) one or more alkoxylated alcohols of formula
RO(C2H4O)x(C3H6O)yZ
xe2x80x83wherein R is straight or branched C4-C40 alkyl; x is 0 to about 25; y is less than 1 to about 50 and Z is H or the residue of an organic acid, and
b) an effective emulsifying amount of one or more anionic surfactants.
The amount of emulsion effective to inhibit foaming may be empirically determined by one of ordinary skill in the art of papermaking, based on the characterstics of the pulp slurry being treated. Typically, from about 0.01 lb/ton to about 5.0 lb/T, based on polymer solids, of the aqueous emulsion is added to the pulp slurry.